Too much sugar turns off gene that controls the effects of sex steroids

Aug 20, 2012

Eating too much fructose and glucose can turn off the gene that regulates the levels of active testosterone and estrogen in the body, shows a new study in mice and human cell cultures that’s published this month in the Journal of Clinical Investigation. This discovery reinforces public health advice to eat complex carbohydrates and avoid sugar. Table sugar is made of glucose and fructose, while fructose is also commonly used in sweetened beverages, syrups, and low-fat food products. Estimates suggest North Americans consume 33 kg of refined sugar and an additional 20 kg of high fructose corn syrup per person per year.

Glucose and fructose are metabolized in the liver. When there’s too much sugar in the

diet, the liver converts it to lipid. Using a mouse model and human liver cell cultures, the

scientists discovered that the increased production of lipid shut down a gene called

SHBG (sex hormone binding globulin), reducing the amount of SHBG protein in the

blood. SHBG protein plays a key role in controlling the amount of testosterone and

estrogen that’s available throughout the body. If there’s less SHBG protein, then more

testosterone and estrogen will be released throughout the body, which is associated with

an increased risk of acne, infertility, polycystic ovaries, and uterine cancer in overweight

women. Abnormal amounts of SHBG also disturb the delicate balance between estrogen

and testosterone, which is associated with the development of cardiovascular disease,

especially in women.

“We discovered that low levels of SHBG in a person’s blood means the liver’s metabolic

state is out of whack – because of inappropriate diet or something that’s inherently wrong

with the liver – long before there are any disease symptoms,” says Dr. Geoffrey

Hammond, the study’s principal investigator, scientific director of the Child & Family

Research Institute in Vancouver, Canada, and professor in the Department of Obstetrics